1. Field of the Invention
The present invention relates generally to a method and system for depositing an insulating film having a low dielectric constant of a silicon oxide film to which a predetermined material is added.
2. Description of the Prior Art
As a conventional interlayer dielectric film of a device, a silicon oxide film (SiO2 film) has been used. As one of techniques for depositing an SiO2 film, there is a method using a parallel plate plasma processing system for applying a high-frequency power between top-and bottom electrodes, which are parallel to each other, to produce plasma to deposit a thin film with the plasma. As the prior art using this system, there is, e.g., Japanese Patent No. 2,774,367. This patent disclose that the frequency of a high-frequency power supply connected to the top electrode is set to be 100 MHz or higher, and the frequency of a high-frequency power supply connected to the bottom electrode is set to be in the range of from 10 MHz to 50 MHz, to apply a high frequency power between both electrodes to produce the plasma of a silane containing gas and oxygen gas to deposit an SiO2 film.
In recent years, in order to further accelerate the operation of devices, it is required that the dielectric constant (relative dielectric constant) of an interlayer dielectric film is lowered. The dielectric constant (relative dielectric constant) of an SiO2 film having been conventionally used is about 0.4 which can not cope with such a request, so that it is desired that an insulating film having a low dielectric constant is provided. Therefore, the inventor has studied insulating films which contain an SiO2 film as an principal component and other components and which has a lower dielectric constant than the SiO2 film, e.g., SiOF films containing fluorine (F) and SiCHO films containing carbon (C) and hydrogen (H).
However, if an insulating film of this type is deposited by the above described prior art method, there is a problem in that a large amount of the other components are eliminated from the film during a heat treatment which will be carried out later with respect to a semiconductor wafer. For example, if F is eliminated from the SiOF film, a metal wiring is corroded, and if H (hydrogen) is eliminated from the SiCHO film, H is accumulated between the SiCHO film and the metal wiring, so that the metal wiring is peeled off. It is guessed that the reason for this is that the energy of ions is too small to decrease the number of dangling bonds (unbonded hands), so that the other components (mixed components), such as F mixed in the SiO2 film, are easily eliminated.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a plasma deposition method and system capable of depositing a high quality insulating film having a low dielectric constant.
In order to accomplish the aforementioned and other objects, according to one aspect of the present invention, a method and system for depositing a silicon oxide film is provided, which contains a predetermined material having a lower dielectric constant than the dielectric constant of a silicon oxide film (SiO2 film), on an object to be processed, using a so-called parallel plate plasma processing system, wherein the frequency of a high-frequency power applied to a first electrode, on which the object to be mounted, is set to be in the range of from 2 MHz to 9 MHz, and the frequency of a high-frequency power applied to a second electrode is set to be 50 MHz or higher. As the silicon oxide film containing the predetermined material, there are F containing films (SiOF films), C and H containing films (SiCHO films), and C, H and N containing films (SiCHNO films). According to the present invention, since the energy of ions during processing has a moderate magnitude, the eliminated amount of the predetermined material is small, and the network bonds are sufficiently formed in the film, so that it is possible to obtain a high quality insulating film.